WO2020186655A1 - 基于服务类型的车载自组织网络中内容转发节点选择方法 - Google Patents
基于服务类型的车载自组织网络中内容转发节点选择方法 Download PDFInfo
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- WO2020186655A1 WO2020186655A1 PCT/CN2019/094707 CN2019094707W WO2020186655A1 WO 2020186655 A1 WO2020186655 A1 WO 2020186655A1 CN 2019094707 W CN2019094707 W CN 2019094707W WO 2020186655 A1 WO2020186655 A1 WO 2020186655A1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
- B60W40/10—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to vehicle motion
- B60W40/105—Speed
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/30—Services specially adapted for particular environments, situations or purposes
- H04W4/40—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P]
- H04W4/44—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P] for communication between vehicles and infrastructures, e.g. vehicle-to-cloud [V2C] or vehicle-to-home [V2H]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/30—Services specially adapted for particular environments, situations or purposes
- H04W4/40—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P]
- H04W4/46—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P] for vehicle-to-vehicle communication [V2V]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W40/00—Communication routing or communication path finding
- H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W40/00—Communication routing or communication path finding
- H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
- H04W40/20—Communication route or path selection, e.g. power-based or shortest path routing based on geographic position or location
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W84/00—Network topologies
- H04W84/18—Self-organising networks, e.g. ad-hoc networks or sensor networks
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W2554/00—Input parameters relating to objects
- B60W2554/40—Dynamic objects, e.g. animals, windblown objects
- B60W2554/404—Characteristics
- B60W2554/4041—Position
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W2554/00—Input parameters relating to objects
- B60W2554/40—Dynamic objects, e.g. animals, windblown objects
- B60W2554/404—Characteristics
- B60W2554/4049—Relationship among other objects, e.g. converging dynamic objects
Definitions
- the invention belongs to the field of communication technology, and in particular relates to a method for selecting content forwarding nodes in a vehicle-mounted ad hoc network based on service types.
- VANET vehicular self-organizing network
- ITS intelligent transportation systems
- VANET regards vehicle nodes and road infrastructure as network nodes, and mainly realizes the communication between vehicles (V2V, Vehicle-to-Vehicle Communication) and the communication between vehicles and roadside facilities (V2I, Vehicle-to-Infrastructure Communication), forming
- V2V Vehicle-to-Vehicle Communication
- V2I Vehicle-to-Infrastructure Communication
- VANET Due to the high mobility of vehicles, VANET has the characteristics of frequent changes in the network topology.
- the general MANET protocol is prone to network interruption, high delay, high packet loss rate and other problems, which cannot meet the needs of VANET. Therefore, the protocol design of VANET has become a research hotspot to solve these problems.
- VANETs the high-speed movement of vehicles leads to large changes in the network topology. Vehicles that were within their own communication range at the previous moment are likely to drive out of the communication range at the next moment, and the communication link status is unstable.
- the request information forwarding strategy in VANETs when the request information reaches the vehicle with the content, the vehicle will follow the original path of the request information and return to the original request vehicle. However, due to the high-speed mobility of the vehicle, the vehicles participating in the collaboration in the request information arrival path may have left each other's communication range during the content return process, and the communication link link cannot be established. The content may not arrive smoothly by returning through the original route.
- the initial content request vehicle there may also be a better forwarding path than the original path to the original request vehicle according to the requested information.
- Purpose of the invention In order to overcome the shortcomings in the prior art, to provide a method for selecting content forwarding nodes in a vehicle-mounted ad hoc network based on service types, which solves how to dynamically based on the current network topology and the type of service information that needs to be transmitted Select the appropriate content forwarding node to achieve the purpose of improving the successful arrival rate of content, effectively using limited channel resources, reducing transmission delay, and improving network performance.
- the present invention provides a method for selecting content forwarding nodes in a vehicle-mounted ad hoc network based on service types, including the following steps:
- S1 Calculate the bandwidth occupancy scale factor according to the requested content information type and the bandwidth occupancy of neighboring vehicles that can be forwarded within the one-hop transmission range;
- S2 Define the virtual arrival time of the candidate forwarding vehicle to the initial requesting vehicle according to the distance between the neighboring vehicle and the initial requesting vehicle and the driving speed of the neighboring vehicle;
- S4 Select the forwarding node according to the forwarding node influence factor.
- the content vehicle y receives the request information at time t, obtains the requested content type according to the name of the requested content contained in the received request information, and determines the bandwidth BW and the occupied time t need required to send the content;
- V i is calculated idle vehicle size available bandwidth BW free (V i);
- step S2 the method of defining the virtual arrival time in step S2 is as follows:
- step S3 the calculation method of the forwarding node influence factor in step S3 is as follows:
- the influence factor of the selection of forwarding node vehicle i is calculated among them, with They are the normalized values of the bandwidth occupancy scale factor K i and the virtual arrival time T (i,x) , which represent the influence of the bandwidth and moving speed of the candidate forwarding vehicle on the selection of the forwarding vehicle, and F i represents the successful selection of the forwarding node Possibility.
- a factor of -1 indicates that the impact factor is negatively related to the possibility of successfully selecting a forwarding vehicle.
- the method for selecting the forwarding node in step S4 is specifically: selecting the vehicle with the largest impact factor among neighboring vehicles of vehicle y as the forwarding node, and adding the vehicle ID, required bandwidth, and occupation time information to the RFR The information is sent out, and when the forwarding vehicle receives the RFR information, it updates its own channel bandwidth idle situation at the current moment.
- the vehicle updates its own channel bandwidth idle condition after receiving the RFR information as follows:
- S4-1 The vehicle that receives the RFR information first judges whether it is selected as a forwarding vehicle, if it is, judge whether the free bandwidth is greater than the bandwidth threshold, if not, do nothing;
- S4-2 If the free bandwidth is not greater than the bandwidth threshold, send an ACK message to inform that it cannot be the forwarding vehicle; if the free bandwidth is greater than the bandwidth threshold, continue to determine whether there are multiple content vehicles to choose itself, if so, choose the distance to itself The farthest content vehicle is used as the forwarding vehicle, if not, confirm it as the forwarding vehicle;
- the forwarding vehicle sends the ACK information to the content vehicle, the content vehicle sends the content information after receiving it, and the forwarding vehicle forwards it after receiving it.
- step S4-3 when the forwarding vehicle performs forwarding in step S4-3, it is judged whether the number of selections exceeds the threshold, if not, skip to step S1 after forwarding; if so, give up sending the content.
- the basic idea of the present invention is that after the content vehicle receives the request information, it comprehensively selects the content forwarding node according to the neighbor vehicle's available transmission bandwidth table maintained by itself, in combination with the vehicle's location, driving direction, and driving speed.
- the requested information reaches the vehicle with content, first determine whether the initial request vehicle is within its own communication range. If it is, the content data information will be sent directly. If not, the vehicle with content will determine what is needed for transmission according to the type of content information requested.
- the bandwidth size and the bandwidth occupancy of neighboring vehicles that can be forwarded within one hop transmission range calculate the bandwidth occupancy scale factor; then define the candidate forwarding vehicle to the initial The virtual arrival time of the requested vehicle; comprehensive bandwidth occupancy scale factor and virtual arrival time, calculate the influence factor of the candidate forwarding vehicle, and determine the content forwarding node according to the size of the influence factor.
- the determined forwarding vehicle ID is added to the RFR information packet, and the channel bandwidth and occupation time to be used are added at the same time.
- the forwarding vehicle receives the RFR information, it updates its own channel bandwidth idle situation at the current moment.
- the content vehicle After the content vehicle receives the request information, it needs to comprehensively select the content forwarding node according to the neighbor vehicle's available transmission bandwidth table maintained by itself, combined with factors such as the location, driving direction, and driving speed of the vehicle, so as to improve the transmission quality while ensuring the content Arrived as soon as possible.
- the invention considers the characteristics of different service types in the vehicle ad hoc network for different bandwidth requirements, defines the bandwidth proportional occupancy factor of the forwarding node, and at the same time, combines the characteristics of the rapid change of the vehicle self-organizing network topology to define the virtual arrival time of the forwarding node.
- the analysis of these two parameters of the forwarding node obtains the influence factors of all optional forwarding nodes in the next hop, which provides a basis for selecting forwarding nodes for content information.
- the invention selects the forwarding node according to the bandwidth occupancy condition and the node position moving speed, can effectively avoid the network time delay caused by the network topology change, and improve the success rate of content information forwarding.
- the present invention has the following advantages:
- Figure 1 is a flow diagram of a method for selecting content forwarding nodes in a vehicle-mounted ad hoc network based on service types
- Figure 2 is a schematic diagram of the comparison of content information to reach power with the number of vehicles
- Figure 3 is a comparison diagram of the average path length required to transmit successful information with the number of vehicles.
- the present invention provides a method for selecting content forwarding nodes in a vehicle-mounted ad hoc network based on service types, as shown in Fig. 1, and its overall flow includes the following steps:
- the content vehicle y receives the request information at time t, obtains the requested content type according to the name of the requested content contained in the received request information, and determines the bandwidth BW and the occupied time t need required to send the content;
- the influence factor of the selection of forwarding node vehicle i is calculated among them, with Respectively bandwidth scaling factor K i values and the virtual normalized arrival time T (i, x), Indicates the degree of influence of the candidate forwarding vehicle's bandwidth and moving speed on the selection of forwarding vehicles.
- F i represents the probability of successfully selecting a forwarding node. For example, a factor of -1 indicates that the influence factor is negatively correlated with the possibility of successfully selecting a forwarding vehicle.
- the vehicle that receives the RFR information first judges whether it is selected as the forwarding vehicle, if it is, judge whether the free bandwidth is greater than the bandwidth threshold, if not, then do nothing.
- the forwarding vehicle sends the ACK message to the content vehicle.
- the content vehicle sends the content information after receiving it, and the forwarding vehicle forwards it after receiving it.
- the forwarding vehicle judges whether the number of selections exceeds the threshold, if not, then jump to Step S1; if yes, give up sending the content.
- the content vehicle After the content vehicle receives the requested information, it comprehensively selects the content forwarding node according to the available transmission bandwidth table of neighboring vehicles maintained by itself, combined with factors such as the location, driving direction, and driving speed of the vehicle;
- the requested information arrives at the vehicle with content, first determine whether the initial request vehicle is within its own communication range. If it is, the content data information will be sent directly. If not, the vehicle with content will determine the transmission according to the requested content information type. The required bandwidth and the bandwidth occupancy of neighboring vehicles that can be forwarded within one hop transmission range, calculate the bandwidth occupancy scale factor; then define candidate forwarding vehicles based on the distance between the neighboring vehicle and the initial requesting vehicle and the driving speed of the neighboring vehicle The virtual arrival time of the vehicle to the initial request;
- Figure 2 is a schematic comparison diagram of the method of the present invention and the method of directly returning to the original path between the content information to the achieved power and the number of vehicles.
- the content of the method of the present invention is significantly better than the direct pressing The method to return to the original path. This is due to the movement of vehicles in the network.
- vehicles that have requested information forwarding may have moved out of the communication range, and communication links cannot be established for content information transmission, and the content arrival rate is low.
- the content forwarding node selection method proposed by the present invention avoids content loss caused by vehicle movement, and takes into account different types of services, and also avoids content transmission failures caused by different bandwidth requirements, so the success rate is higher. .
- the performance of the algorithm proposed in the present invention gradually improves, because under the premise that the number of content requests remains unchanged, the more vehicles in the network, the more vehicles that can be forwarded, the forwarding success rate increases, and the content reaches the power Also improved.
- the comparison algorithm performance of the existing methods increases with the increase of the number of vehicles in the range slower than the proposed algorithm, because the increase in the number of vehicles cannot solve the problem of content transmission failure caused by vehicle movement, so the content reaches the power requirement. It is significantly lower than the method of the present invention.
- Fig. 3 is a schematic diagram of the comparison of the average path length required to successfully transmit information with the number of vehicles. It can be seen that the average path length required for the method of the present invention to successfully transmit information is smaller than the original path return method. Because due to the movement of the vehicle node, there may be better routes than the original route for the requested information to reach the content vehicle. The method of the present invention can discover and utilize these better routes, while the existing method can only return to the original route.
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Abstract
本发明公开了一种基于服务类型的车载自组织网络中内容转发节点选择方法，包括如下步骤：根据请求的内容信息类型，以及一跳传输范围内可进行转发的邻居车辆的带宽占用情况，计算带宽占用比例因子；根据邻居车辆与初始请求车辆间的距离和邻居车辆的行驶速度，定义候选转发车辆到初始请求车辆的虚拟到达时间；根据带宽占用比例因子和虚拟到达时间，计算转发节点影响因子；根据转发节点影响因子对转发节点进行选择。本发明根据带宽占用情况和节点位置移动速度进行转发节点选择，可以有效的避免由于网络拓扑变化造成的网络时延，提高内容信息转发的成功率，从而有效地提高内容数据包的成功到达率，降低传输时延，提升网络性能。
Description
本发明属于通信技术领域，具体涉及一种基于服务类型的车载自组织网络中内容转发节点选择方法。
车载自组织网络(VANET)作为移动自组织网络(MANET)的一个研究方向，在智能交通系统(ITS)中有着重要的应用。VANET将车辆节点与道路基础设施作为网络节点，主要实现车辆间通信(V2V，Vehicle-to-Vehicle Communication)和车辆与路边设施之间的通信(V2I，Vehicle-to-Infrastructure Communication)，构成了实时通信的移动网络，提高了交通的安全性和管理效率，同时也为车辆驾驶提供了更多的服务。由于车辆的高移动型，VANET具有网络拓扑频繁变化的特性，一般的MANET协议在VANET场景下，容易产生网络中断，高时延，高丢包率等问题，无法满足VANET的需求。所以VANET的协议设计成为了解决这些问题的研究热点。
在VANETs中，车辆的高速移动导致网络拓扑变化较大，上一时刻还在自身通信范围内的车辆很可能下一时刻就驶出了通信范围，通信链路状态不稳定。VANETs中的请求信息转发策略，当请求信息到达拥有内容的车辆时，该车辆将按照请求信息到达路径原路返回到达初始请求车辆。但由于车辆的高速移动性，可能造成请求信息到达路径中参与协作的车辆在内容返回的过程中已经离开彼此的通信范围，无法建立通信链路链接，内容通过原路返回的方式可能无法顺利到达初始内容请求车辆；也可能存在比按照请求信息到达路径原路返回到达初始请求车辆更优的转发路径。
所以，需要一个新的技术方案来解决上述问题。
发明内容
发明目的：为了克服现有技术中存在的不足，提供一种基于服务类型的车载自组织网络中内容转发节点选择方法，其解决了如何根据当前网络拓扑状况，以及需要传输的业务信息的类型动态的选择合适的内容转发节点，以达到提高内容的成功到达率，有效的利用有限的信道资源，降低传输时延，提升网络性能的目的。
技术方案：为实现上述目的，本发明提供一种基于服务类型的车载自组织网络中内容转发节点选择方法，包括如下步骤：
S1：根据请求的内容信息类型，以及一跳传输范围内可进行转发的邻居车辆的带宽占用情况，计算带宽占用比例因子；
S2：根据邻居车辆与初始请求车辆间的距离和邻居车辆的行驶速度，定义候选转发车辆到初始请求车辆的虚拟到达时间；
S3：根据步骤S1的带宽占用比例因子和步骤S2的虚拟到达时间，计算转发节点影响因子；
S4：根据转发节点影响因子对转发节点进行选择。
进一步地，所述步骤S1中带宽占用比例因子的计算过程如下：
S1-1：内容车辆y在时刻t收到请求信息，根据收到的请求信息中包含的请求内容的名称，获取请求内容类型，确定发送该内容需要占用的带宽大小BW和占用时长t
need；
S1-2：车辆y计算车辆V
i的空闲可用带宽大小BW
free(V
i)；
S1-3：车辆y根据确定的BW、总的带宽BW
total及邻居车辆的空闲带宽计算得到车辆i的带宽占用比例因子
其中i＝(1,2,…,N)，N为车辆y的邻居车辆总数。
进一步地，所述步骤S2中虚拟到达时间的定义方式如下：
S2-1：候选转发节点为内容车辆y的一跳邻居车辆，计算候选转发车辆与目的车辆x间的距离D
(i,x)＝|X
i-X
x|，其中，X
i、X
x分别为车辆i、x的横坐标，车辆i为车辆y的邻居车辆；
S2-2：根据车辆行驶方向的不同，当车辆i与车辆x的行驶方向相同时，若车辆i的速度v
i小于车辆x的速度v
x，将车辆i从候选转发节点中去除，若车辆i的速度v
i大于车辆x的速度v
x，则虚拟到达时间
当车辆i与车辆x的行驶方向相反时，若两个车辆互相远离时，将车辆i从候选转发节点中去除，若两个车辆相互靠近时，虚拟到达时间
进一步地，所述步骤S3中转发节点影响因子的计算方法如下：
设车辆y的一跳邻居车辆数目为N，车辆i为其中一个邻居车辆，根据转发节点的带宽占用比例因子和虚拟到达时间，计算得到转发节点车辆i选择的影响因子
其中，
和
分别为带宽占用比例因子K
i和虚拟到达时间T
(i,x)归一化后的值，表示候选转发车辆的带宽和移动速度对于选择转发车辆选择的影响程度，F
i表示成功选择转发节点的可能性。比如因子-1表示影响因子与成功选择转发车辆的可能性呈现负相关。
进一步地，所述步骤S4中转发节点的选择方法具体为：选择车辆y的邻居车辆中影响因子最大的车辆为其转发节点，将该车辆的ID、所需带宽大小、占用时长信息添加到RFR信息中发送出去，当转发车辆收到RFR信息后，更新当前时刻的自身信道带宽空闲情况。
进一步地，所述步骤S4中车辆收到RFR信息后对于自身信道带宽空闲情况的更新如下：
S4-1：收到RFR信息的车辆首先判断自身是否被选为转发车辆，如果是，判断空闲带宽是否大于带宽阀值，如果否，则不做任何操作；
S4-2：如果空闲带宽不大于带宽阀值，则发送ACK信息告知无法成为其转发车辆；如果空闲带宽大于带宽阀值，则继续判断是否有多个内容车辆选择自身，如果是，选择距离自身最远的内容车辆作为转发车辆，如果否，则确认其成为转发车辆；
S4-3：转发车辆发送ACK信息给内容车辆，内容车辆收到后发送内容信息，转发车辆收到后进行转发。
进一步地，所述步骤S4-3中转发车辆进行转发时，判断选择次数是否超过阀值，如果否，转发后跳转至步骤S1；如果是，则放弃内容的发送。
本发明的基本思路是在内容车辆收到请求信息后，根据自身维持的邻居车辆可用传输带宽表，结合车辆的位置、行驶方向和行驶速度等因素，综合选择内容转发节点。当请求信息到达有内容的车辆时，先判断初始请求车辆是否在自身通信范围内，若在，则直接发送内容数据信息，若不在，则有内容的车辆根据请求的内容信息类型确定传输需要的带宽大小，以及一跳传输范围内可进行转发的邻居车辆的带宽占用情况，计算带宽占用比例因子；再根据邻居车辆与初始请求车辆间的距离和邻居车辆的行驶速度，定义候选转发车辆到初始请求车辆的虚拟到达时间；综合带宽占用比例因子与虚拟到达时间，计算候选转发车辆的影响因子，根据影响因子的大小，确定内容转发节点。将确定的转发车辆ID添加到RFR信息包中，同时加入要使用的信道带宽和占用时长。当转发车辆收到RFR信息后，更新当前时刻的自身信道带宽空闲情况。
本发明在内容车辆收到请求信息后，需要根据自身维持的邻居车辆可用传输带宽表，结合车辆的位置、行驶方向和行驶速度等因素，综合选择内容转发节点，提高传输质量的同时，保证内容的尽快到达。
本发明考虑车载自组织网络中不同服务类型对于带宽要求不同的特点，定义了转发节点的带宽比例占用因子，同时结合车载自组织网络拓扑变化快的特点，定义了转发节点的虚拟到达时间，通过对转发节点这两个参数的分析，得到下一跳所有可选转发节点的影响因子，为内容信息选择转发节点提供依据。
本发明根据带宽占用情况和节点位置移动速度进行转发节点选择，可以有效的避免由于网络拓扑变化造成的网络时延，提高内容信息转发的成功率。
有益效果：本发明与现有技术相比，具备如下优点：
1、考虑了发送的业务类型以及转发节点的带宽占用情况，避免了由于业务带宽需求造成的传输失败，提高了转发成功率，降低了传输时延。
2、考虑了转发车辆的位置信息和速度信息，避免了由于车载自组织网络拓扑结构变化快而带来的转发节点丢失，车辆移除一跳通信范围的问题，提高了业务信息的转发成功率，同时根据车辆速度选择转发节点也提升了业务信息转发速度，降低了传输时延。
图1为基于服务类型的车载自组织网络中内容转发节点选择方法流程示意图；
图2为内容信息到达成功率随车辆数变化对比示意图；
图3为传输成功信息所需平均路径长度随车辆数变化对比示意图。
下面结合附图和具体实施例，进一步阐明本发明。
本发明提供一种基于服务类型的车载自组织网络中内容转发节点选择方法，如图1所示，其总体流程包括如下步骤：
1)在收到请求信息的有内容车辆中，判断初始请求车辆是否在自身通信范围之内，如果是，则直接发送内容数据包；如果否，则进入下个步骤。
2)根据请求的内容信息类型，以及一跳传输范围内可进行转发的邻居车辆的带宽占用情况，计算带宽占用比例因子：
2.1)内容车辆y在时刻t收到请求信息，根据收到的请求信息中包含的请求内容的名称，获取请求内容类型，确定发送该内容需要占用的带宽大小BW和占用时长t
need；
2.2)车辆y计算车辆V
i的空闲可用带宽大小BW
free(V
i)；
2.3)车辆y根据确定的BW、总的带宽BW
total及邻居车辆的空闲带宽计算得到车辆i的带宽占用比例因子
其中i＝(1,2,…,N)，N为车辆y的邻居车辆总数。
3)根据邻居车辆与初始请求车辆间的距离和邻居车辆的行驶速度，定义候选转发车辆到初始请求车辆的虚拟到达时间，其定义方式具体如下：
3.1)候选转发节点为内容车辆y的一跳邻居车辆，计算候选转发车辆与目的车辆x间的距离D
(i,x)＝|X
i-X
x|，其中，X
i、X
x分别为车辆i、x的横坐标，车辆i为车辆y的 邻居车辆；
3.2)根据车辆行驶方向的不同，当车辆i与车辆x的行驶方向相同时，若车辆i的速度v
i小于车辆x的速度v
x，表明车辆i距离车辆x越来越远，将车辆i从候选转发节点中去除，若车辆i的速度v
i大于车辆x的速度v
x，则虚拟到达时间
当车辆i与车辆x的行驶方向相反时，若两个车辆互相远离时，表明两个车辆无法在接下来一段时间相遇，将车辆i从候选转发节点中去除，若两个车辆相互靠近时，虚拟到达时间
4)根据步骤S1的带宽占用比例因子和步骤S2的虚拟到达时间，计算转发节点影响因子：
设车辆y的一跳邻居车辆数目为N，车辆i为其中一个邻居车辆，根据转发节点的带宽占用比例因子和虚拟到达时间，计算得到转发节点车辆i选择的影响因子
其中，
和
分别为带宽占用比例因子K
i和虚拟到达时间T
(i,x)归一化后的值，
表示候选转发车辆的带宽和移动速度对于选择转发车辆选择的影响程度，F
i表示成功选择转发节点的可能性，比如因子-1表示影响因子与成功选择转发车辆的可能性呈现负相关。
5)选择车辆y的邻居车辆中影响因子最大的车辆为其转发节点，将该车辆的ID、所需带宽大小、占用时长信息添加到RFR信息中发送出去。
6)收到RFR信息的车辆首先判断自身是否被选为转发车辆，如果是，判断空闲带宽是否大于带宽阀值，如果否，则不做任何操作。
7)如果空闲带宽不大于带宽阀值，则发送ACK信息告知无法成为其转发车辆；如果空闲带宽大于带宽阀值，则继续判断是否有多个内容车辆选择自身，如果是，选择距离自身最远的内容车辆作为转发车辆，如果否，则确认其成为转发车辆。
8)转发车辆发送ACK信息给内容车辆，内容车辆收到后发送内容信息，转发车辆收到后进行转发，转发车辆进行转发时，判断选择次数是否超过阀值，如果否，转发后跳转至步骤S1；如果是，则放弃内容的发送。
根据上述方法步骤，本发明方法步骤可归纳为如下内容：
1、内容车辆收到请求信息后，根据自身维持的邻居车辆可用传输带宽表，结合车 辆的位置、行驶方向和行驶速度等因素，综合选择内容转发节点；
2、当请求信息到达有内容的车辆时，先判断初始请求车辆是否在自身通信范围内，若在，则直接发送内容数据信息，若不在，则有内容的车辆根据请求的内容信息类型确定传输需要的带宽大小，以及一跳传输范围内可进行转发的邻居车辆的带宽占用情况，计算带宽占用比例因子；再根据邻居车辆与初始请求车辆间的距离和邻居车辆的行驶速度，定义候选转发车辆到初始请求车辆的虚拟到达时间；
3、综合带宽占用比例因子与虚拟到达时间，计算候选转发车辆的影响因子，根据影响因子的大小，确定内容转发节点，将确定的转发车辆ID添加到RFR信息包中，同时加入要使用的信道带宽和占用时长，当转发车辆收到RFR信息后，更新当前时刻的自身信道带宽空闲情况。
本实施例中将本发明方法和直接按原路径返回的现有方法进行对比分析，具体结果如下：
如图2所示为本发明方法和直接按原路径返回方法在内容信息到达成功率随车辆数的变化示意对比图，根据图1可知，本发明方法的内容到达成功率要明显优于直接按原路径返回的方法。这是由于网络中车辆的移动，造成在业务返回过程中，之前进行过请求信息转发的车辆可能已经移出了通信范围，无法建立通信链路进行内容信息的传输，内容到达率较低。而通过本发明提出的内容转发节点选择方法，避免了由于车辆移动而造成的内容丢失，而且考虑了服务类型的不同，也避免了因为不同带宽需求而造成的内容传输失败，因此成功率较高。随着车辆数的增加，本发明提出的算法性能逐渐提升，因为在内容请求数量不变的前提下，网络中车辆数越多，可选转发车辆越多，转发成功率提高，内容到达成功率也随之提高。而现有方法的对比算法性能随着范围内车辆数的增加提升趋势慢于所提算法，因为车辆数的增加不能解决因为车辆移动而造成的内容传输失败的问题，所以其内容到达成功率要明显低于本发明方法。
如图3所示为成功传输信息所需平均路径长度随车辆数变化对比示意图，可以看出本发明的方法成功传输信息所需平均路径长度要小于原路径返回方法。因为由于车辆节点的移动，可能存在比请求信息到达内容车辆的原路径更优的路径，本发明方法能够发现和利用这些更优路径，而现有方法只能原路径返回。
Claims (7)
- 基于服务类型的车载自组织网络中内容转发节点选择方法，其特征在于：包括如下步骤：S1：根据请求的内容信息类型，以及一跳传输范围内可进行转发的邻居车辆的带宽占用情况，计算带宽占用比例因子；S2：根据邻居车辆与初始请求车辆间的距离和邻居车辆的行驶速度，定义候选转发车辆到初始请求车辆的虚拟到达时间；S3：根据步骤S1的带宽占用比例因子和步骤S2的虚拟到达时间，计算转发节点影响因子；S4：根据转发节点影响因子对转发节点进行选择。
- 根据权利要求1所述的基于服务类型的车载自组织网络中内容转发节点选择方法，其特征在于：所述步骤S1中带宽占用比例因子的计算过程如下：S1-1：内容车辆y在时刻t收到请求信息，根据收到的请求信息中包含的请求内容的名称，获取请求内容类型，确定发送该内容需要占用的带宽大小BW和占用时长t need；S1-2：车辆y计算车辆V i的空闲可用带宽大小BW free(V i)；S1-3：车辆y根据确定的BW、总的带宽BW total及邻居车辆的空闲带宽计算得到车辆i的带宽占用比例因子其中i＝(1,2,…,N)，N为车辆y的邻居车辆总数。
- 根据权利要求1或2所述的基于服务类型的车载自组织网络中内容转发节点选择方法，其特征在于：所述步骤S2中虚拟到达时间的定义方式如下：S2-1：候选转发节点为内容车辆y的一跳邻居车辆，计算候选转发车辆与目的车辆x间的距离D (i,x)＝|X i-X x|，其中，X i、X x分别为车辆i、x的横坐标，车辆i为车辆y的邻居车辆；S2-2：根据车辆行驶方向的不同，当车辆i与车辆x的行驶方向相同时，若车辆i的速度v i小于车辆x的速度v x，将车辆i从候选转发节点中去除，若车辆i的速度v i大于车辆x的速度v x，则虚拟到达时间当车辆i与车辆x的行驶方向相反时，若两个车辆互相远离时，将车辆i从候选转发节点中去除，若两个车辆相互靠近时，虚拟到达时间
- 根据权利要求1所述的基于服务类型的车载自组织网络中内容转发节点选择方 法，其特征在于：所述步骤S3中转发节点影响因子的计算方法如下：设车辆y的一跳邻居车辆数目为N，车辆i为其中一个邻居车辆，根据转发节点的带宽占用比例因子和虚拟到达时间，计算得到转发节点车辆i选择的影响因子其中，
和
分别为带宽占用比例因子K i和虚拟到达时间T (i,x)归一化后的值，表示候选转发车辆的带宽和移动速度对于选择转发车辆选择的影响程度，F i表示成功选择转发节点的可能性。
- 根据权利要求1所述的基于服务类型的车载自组织网络中内容转发节点选择方法，其特征在于：所述步骤S4中转发节点的选择方法具体为：选择车辆y的邻居车辆中影响因子最大的车辆为其转发节点，将该车辆的ID、所需带宽大小、占用时长信息添加到RFR信息中发送出去，当转发车辆收到RFR信息后，更新当前时刻的自身信道带宽空闲情况。
- 根据权利要求5所述的基于服务类型的车载自组织网络中内容转发节点选择方法，其特征在于：所述步骤S4中车辆收到RFR信息后对于自身信道带宽空闲情况的更新如下：S4-1：收到RFR信息的车辆首先判断自身是否被选为转发车辆，如果是，判断空闲带宽是否大于带宽阀值，如果否，则不做任何操作；S4-2：如果空闲带宽不大于带宽阀值，则发送ACK信息告知无法成为其转发车辆；如果空闲带宽大于带宽阀值，则继续判断是否有多个内容车辆选择自身，如果是，选择距离自身最远的内容车辆作为转发车辆，如果否，则确认其成为转发车辆；S4-3：转发车辆发送ACK信息给内容车辆，内容车辆收到后发送内容信息，转发车辆收到后进行转发。
- 根据权利要求6所述的基于服务类型的车载自组织网络中内容转发节点选择方法，其特征在于：所述步骤S4-3中转发车辆进行转发时，判断选择次数是否超过阀值，如果否，转发后跳转至步骤S1；如果是，则放弃内容的发送。
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| Publication number | Publication date |
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| CN109831758A (zh) | 2019-05-31 |
| CN109831758B (zh) | 2020-12-04 |
| US20230219581A1 (en) | 2023-07-13 |
| US11834055B2 (en) | 2023-12-05 |
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